CVE-2025-39833

Kernel warning via uninitialized hfcpci timer

Published Sep 16, 2025 · Updated Sep 16, 2025

Use of an uninitialized timer in Linux hfcpci allows local users to trigger a kernel warning by unloading the module. HFC_cleanup synchronously deletes hfc_tl even though the timer was never initialized, while the driver manually changes its timeout instead of using mod_timer. Reachability requires the hfcpci module, CONFIG_DEBUG_OBJECTS_TIMERS, and privilege to unload a kernel module; the published trace demonstrates a warning rather than a crash.

CVSS severity5.5
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use of an uninitialized timer in Linux hfcpci allows local users to trigger a kernel warning by unloading the module. HFC_cleanup synchronously deletes hfc_tl even though the timer was never initialized, while the driver manually changes its timeout instead of using mod_timer. Reachability requires the hfcpci module, CONFIG_DEBUG_OBJECTS_TIMERS, and privilege to unload a kernel module; the published trace demonstrates a warning rather than a crash.

The record

CVE
CVE-2025-39833
Published
Sep 16, 2025
Updated
Sep 16, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-908
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.29
  2. Affected versionversion=87c5fa1bb42624254a2013cbbc3b170d6017f5d6 <43fc5da8133badf17f5df250ba03b9d882254845
  3. Affected versionversion=87c5fa1bb42624254a2013cbbc3b170d6017f5d6 <97766512a9951b9fd6fc97f1b93211642bb0b220

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.29; version=87c5fa1bb42624254a2013cbbc3b170d6017f5d6 <43fc5da8133badf17f5df250ba03b9d882254845; version=87c5fa1bb42624254a2013cbbc3b170d6017f5d6 <97766512a9951b9fd6fc97f1b93211642bb0b220

Published CVSS scores

5.5CISA ADP VulnrichmentCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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